Electricity, combustible gases, and liquid and solid fuels comprising hydrocarbons are generally used as heating means for heating liquids and solid materials. As a specific heating technique, hydration reactions of calcium oxide, calcium chloride, aluminum or the like are utilized for generating heat (see Japanese Utility Model Application Kokai (Laid-Open) Nos. 60-70235, 61-89332, 62-93654, etc.).
Lately, as a more specific heating medium, there has been proposed a heating device comprising a mixture of red lead oxide powder and silicon powder packed into an elongated tube, such as adopted in a portable boiler-warmer disclosed In Japanese Patent Application Kokai (Laid-Open) No. 52-19358.
Commonly used electricity and combustible gases are very convenient for indoor use, but their outdoor utilization involves many inconveniences. On the other hand, liquid and solid fuels using hydrocarbons are poor in portability since the equipment needs to be enlarged for accelerating the heating speed. Also, difficulties are involved in their outdoor use in a rainy or windy days.
The heating element utilizing heat generation by a hydration reaction of calcium oxide, calcium chloride or aluminum is suited for outdoor use, but it has the drawbacks that the heating speed is relatively slow and that the amount of heat obtainable per unit volume of the calorific agent is very low.
The portable boiler-warmer making use of a calorific agent comprising a mixture of red lead oxide powder and silicon powder packed into an elongated tube (Japanese Pat. Application Kokai No. 52-19358) is fit for either indoor or outdoor use for boiling of water or oil and heat retention. In the case of this device, however, it is unavoidable that the whole casing is relatively enlarged in size. Also, its use is limited to some specific heating purposes, and further the structure of the container is complicated. In addition, the calorific agent itself has the problems of involving troublesomeness in packing it into an elongated tube and the concomitant high production cost. Also, due to the nature of the calorific agent, it needs to apply heating for a while by an electric heater or a lighter for effecting ignition. Thus, a large amount of heat is needed for igniting the calorific agent, which means poor ignitability of the agent.